Luminescence, chemical sensing and mechanical properties of crystalline materials based on lanthanide–sulfonate coordination polymers

Abstract

Lanthanide-coordination polymers (Ln-CPs) constitute relevant compounds for the design of multifunctional materials. Nevertheless, studies devoted to an understanding of the relationships of combined structural–optical–mechanical properties have scarcely been reported. In this work, an exhaustive study of a series of CPs obtained from lanthanide metals, 3-hydroxinaphthalene-2,7-disulfonate (3-OHNDS) and 1,10-phenanthroline (Phen) as ligands is presented. Two crystalline phases were identified with the general formulae [Eu(3-OHNDS)(Phen)(H₂O)]·3H₂O (phase 1-Eu), and [Ln₂(3-OHNDS)₂(Phen)₂(H₂O)]·3H₂O (phase 2-Ln), where Ln³⁺ = Tb, Dy, Ho, Er and Yb. Both phases were characterized by powder and single crystal X-ray diffraction, vibrational and thermal analysis and scanning electron microscopy. Moreover, nanoindentation analysis was performed in order to find the relationships between these structural features and the mechanical properties of the crystalline materials. The photoluminescence (PL) properties of the reported phases were also explored, involving excitation–emission experiments and quantification of color emission. Finally, one compound was selected as a chemical sensor model, exhibiting different optical behaviour in the presence of aromatic molecules, principally towards naphtalene molecules. These results make these compounds promising materials for the elaboration of selective chemical sensors.